Package assembly for thin wafer shipping and method of use

ABSTRACT

A package assembly for thin wafer shipping using a wafer container and a method of use are disclosed. The package assembly includes a shipping container and a wafer container having a bottom surface and a plurality of straps attached thereto placed within the shipping container. The package assembly further includes upper and lower force distribution plates provided within the shipping container positioned respectively on a top side and bottom side thereof.

FIELD OF THE INVENTION

The invention relates to packaging assemblies and, more particularly, toa package assembly for thin wafer shipping using a wafer container and amethod of use.

BACKGROUND

Semiconductor wafer manufacturing utilizes very sophisticated waferprocessing procedures and complicated manufacturing systems. In effortsto reduce the size of the semiconductor package, manufacturers havereduced component sizes including the thickness of the wafer, itself.For example, wafer thinning can be performed by a grinding method toachieve a wafer thickness on the order of 100 microns and less. Thesethin wafers, though, are very fragile and brittle. Of particular concernare thinned wafers with through silicon vias (TSV), which can be about25% as strong as non TSV wafers. For example, as the fracture strengthvaries with the square of wafer thickness, a force to break the thinwafers can be around 1N or less.

Shipping of thin wafers is thus a difficult challenge. Currently, forexample, the wafers are placed into plastic containers for shipping. Inknown implementations, the wafers are manually placed into thecontainers with foam cushions on the bottom and on top and thincleanroom paper dispersed between each wafer. Once placed into thecontainers, a top is placed onto the container. However using thesecontainers and methods of insertion, the thinned wafers are subjected toan unacceptably high risk of damage. For example, when the thin wafersare flexed, whether during the packaging or shipping process, theybecome susceptible to micro-crack generation, which ultimately leads towafer breakage.

Also, existing methods for loading and unloading thin, fragile wafersinto and out of shipping containers is prone to causing wafer breakage.For example, dicing vendors prefer to manually remove thin, fragilewafers instead of extracting them from shipping containers with vacuumwands. However, wafers easily break if they contact the wall of theshipping container while they are being placed into and/or removed fromthe shipping container. This problem will only grow worse as theindustry trends to even thinner wafers.

Accordingly, there exists a need in the art to overcome the deficienciesand limitations described hereinabove.

SUMMARY

In an aspect of the invention, a package assembly comprises a shippingcontainer and a wafer container having a bottom surface and a pluralityof straps attached thereto placed within the shipping container. Thepackage assembly further comprises upper and lower force distributionplates provided within the shipping container positioned respectively ona top side and bottom side thereof.

In an aspect of the invention, a package assembly comprises a wafercontainer comprising a plurality of straps. The package assembly furthercomprises a stack of wafers interposed with ESD compliant materialsheets positioned within the wafer container. The package assemblyfurther comprises a distribution plate positioned on a top side andbottom side of the stack of wafers. The distribution plates arestructured to: contain the stack of wafers as a unit; and distributeforces across a surface of the stack of wafers.

In an aspect of the invention, a method comprises: spreading straps of awafer container to expose a bottom surface thereof; placing a lowerforce distribution plate on the bottom surface of the wafer container;alternately stacking a plurality of wafers and sheets on the lower forcedistribution plate; placing an upper force distribution plate on anupper sheet of the stack of wafers; lifting the wafer container andplacing it within a shipping container; placing foam cushioning withinthe shipping container to protect the stack of wafers; and sealing theshipping container.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present invention is described in the detailed description whichfollows, in reference to the noted plurality of drawings by way ofnon-limiting examples of exemplary embodiments of the present invention.

FIG. 1 shows a wafer container in accordance with aspects of the presentinvention;

FIG. 2 shows a wafer container in accordance with another aspect of thepresent invention;

FIG. 3 shows a wafer container in accordance with yet another aspect ofthe present invention;

FIG. 4 shows a side view of a wafer container with wafers loadedtherein, in accordance with aspects of the present invention;

FIG. 5 shows a side view of an alternative wafer container with wafersloaded therein, in accordance with additional aspects of the presentinvention;

FIG. 6 shows a top view of the wafer container inserted into a shippingcontainer, in accordance with aspects of the present invention;

FIG. 7 shows a side cross-sectional view of the wafer container insertedwithin a shipping container, in accordance with aspects of the presentinvention; and

FIG. 8 is representative of a packing and unpacking procedure inaccordance with aspects of the present invention.

DETAILED DESCRIPTION

The invention relates to packaging assemblies and, more particularly, toa package assembly for thin wafer shipping using a wafer container and amethod of use. More specifically, the present invention is directed to awafer container (also referred to as a wafer basket or wafer cartridge)for holding thin wafers. Advantageously, the wafer container allowsfragile wafers to be loaded into and unloaded from a shipping containerwithout breakage or damage from contacting the walls of the shippingcontainer. Thus, the present invention prevents breakage of the thinwafers during the shipping process, e.g., packaging and unpackaging ofthe thin wafers.

In embodiments, the wafer container includes straps provided in manydifferent configurations as described herein, which allow the wafercontainer to be packaged into and unpackaged from the shippingcontainer. In embodiments, the straps can be hinged or made of flexiblematerial, any of which configuration has a length extending beyond anupper portion of the shipping container to provide a means for graspingthe straps for such packaging and unpackaging. By using the wafercontainer, the probability of wafer breakage decreases significantlyover existing approaches. In fact, tests have shown that a success rateof 100% can be achieved with shipping sub-100 μm thickness wafers.

In addition to using the wafer container, force distribution plates canbe used within the package assembly to reduce flexing of the thin waferswhile in transit. The force distribution plates are rigid plates placedbelow and above a stack of thin wafers in a container, therebyrestricting flexure of the wafer and reducing wafer breakage. Inembodiments, the force distribution plates can be placed within thewafer container with the stack of wafers. In other embodiments, thestraps can be directly fastened to the force distribution plates, forpackaging into and unpackaging from the shipping container.

FIG. 1 shows a wafer container in accordance with aspects of the presentinvention. In embodiments, the wafer container 10 includes a bottomsurface 12 and a plurality of straps 14. Preferably, the bottom surface12 has a diameter approximate to that of the wafers, e.g., 200 mm, 300mm, etc. The straps 14 can have a hinge 14 a located above a maximumheight of stacked wafers and/or a force distribution plate as describedherein. For example, the hinge 14 a can be at a height of about thetotal height of the stack of wafers with force distribution plates andprotective sheets. In additional or alternative embodiments, the straps14 can be made of a flexible material. It should be understood by thoseof skill in the art that the hinge 14 a can be considered a flexiblefeature of the strap 14. In embodiments, the wafer container 10(including the bottom surface 12 and straps 14) can be made of anyelectrostatic discharge (ESD) compliant material such as, for example,plastic with conductive coatings, TYVEK® (TYVEK is a trademark of DuPontCompany) or other ESD compliant materials.

Still referring to FIG. 1, in embodiments, three or more straps 14 areattached or bonded to the bottom surface 12 of the wafer container 10.In any of the configurations, the straps 14 are preferably locatedequidistance from one another. For example, in the three strapconfiguration, each strap would be located at 120° about thecircumference of the bottom surface 12. The spacing of the straps 14will provide stability to the wafer container 10 during loading andunloading of the wafers into and out of a shipping container,respectively.

FIG. 2 shows a wafer container in accordance with another aspect of thepresent invention. In this aspect of the invention, the wafer container10′ includes straps 14′ with optional tabs 14 a′ and optional slits 16.It should be understood by those of skill in the art that anycombination of the optional tabs 14 a′ and optional slits 16 can beimplemented with the present invention. In embodiments, the optionaltabs 14 a′ provide a mechanism for grasping of the straps 14′ for easeof handling. The optional slits 16, on the other hand, provide amechanism for attaching straps 14′ together when packaging the wafers(and optional force distribution plates). By way of example, a strap canbe inserted within the slit 16 of another strap to secure the strapstogether. In alternative or additional embodiments, reference numeral 16can represent other fastening mechanisms such as, for example, fabrichook-and-loop fasteners (e.g., Velcro®).

FIG. 3 shows a wafer container in accordance with yet another aspect ofthe present invention. In this aspect of the invention, the wafercontainer 10″ includes tabs 18 which provide a lateral cushioning forthe wafers when inserted into a shipping container. The tabs 18 can beprovided about the circumference of the bottom surface 12, and can bemade from any ESD compliant material as already described herein. Inembodiments, the tabs 18 should have a height of about a stack of waferspacked within the wafer container 10″, e.g., the total height of thestack of wafers with force distribution plates and protective sheets.Again, it should be understood by those of skill in the art that anycombination of the optional tabs 14 a′, optional slits 16 and optionaltabs 18 can be implemented with the present invention.

FIG. 4 shows a side view of a wafer container with wafers loadedtherein, in accordance with additional aspects of the present invention.More specifically, FIG. 4 shows the wafer container 10″ of FIG. 3holding a plurality of wafers 20. In this implementation and others, thewafers 20 are placed in the wafer container 10″ and are separated andprotected by sheets of cleanroom paper, TYVEK® or other clean and ESDcompliant material sheets, all of which are designated as referencenumeral 22. The ESD compliant material sheets 22 prevent rubbing andscratching of the wafers 20. As also shown, the tabs 18 have a height ofabout a stack of wafers 20 packed within the wafer container 10″. Itshould be understood by those of skill in the art that the plurality ofwafers 20 can be packed into any of the wafer containers describedherein, in a similar manner.

FIG. 5 shows a side view of an alternative wafer container with wafersloaded therein, in accordance with additional aspects of the presentinvention. In this configuration, the wafer container 10′″ includesstraps 14″ connected directly to a bottom force distribution plate 24.That is, the wafer container 10′″ no longer includes a bottom surface asshown in FIGS. 1-4. The straps 14″ can be bonded to the forcedistribution plate 24 with an adhesive or other bonding mechanism.

In this configuration, the bottom force distribution plate is providedon a bottom of a stack of wafers 20, 22, and a top force distributionplate 24 is provided on a top side the stack of wafers 20, 22.Advantageously, by using the force distribution plates 24 in combinationwith the wafer container (of any aspect of the invention), it is nowpossible to ship upwards of 13 or more 75 micron thin wafers 20, withoutdamage; compared to conventional systems which are able to stack onlysix wafers, with the possibility of damage occurring to some of thosewafers. Accordingly, in aspects of the present invention, the wafercontainer (of FIGS. 1-5) should be sized and structured to accommodateupwards of 13 or more 75 micron thin wafers 20 and two forcedistribution plates 24.

The force distribution plates 24 are reasonably flat and rigid, therebypreventing flexure of the wafers during shipping. The force distributionplates 24 are also sized to fit within a shipping container and wafercontainer of any aspect of the present invention. The force distributionplate 24, for example, can be standard thickness silicon wafers or someother suitable material fabricated into force distribution plates, e.g.,any ESD (electro-static discharge) compliant material such as metaldiscs, plastic discs with conductive coatings or other materials. Theforce distribution plate 24 can have a thickness of about 1 mm to about2 mm; although other dimensions are contemplated by the presentinvention, depending on the material used to fabricate the forcedistribution plate 24.

During shipping, the force distribution plates 24 advantageouslydistribute forces over the entire surface of the wafers, thus reducingthe overall force applied to any single point on the wafer. For example,vibration forces occurring during shipping as well as vertical forcesapplied onto the wafers during packaging and unpackaging can bedistributed over the entire surface of the wafers, thereby reducing oreliminating a larger force being applied to any single point or smallarea on the wafer. In more specific embodiments, the force distributionplate 24 is rigid enough to withstand at least 1N or more of force, toprevent flexure of the thinned wafers. Essentially, the forcedistribution plates 24 act to contain the thin wafers 20 as a unit,allowing them to move only as a unit and distribute all forces acrossthe wafer surface thereby reducing and/or eliminating any damage to thewafers.

FIG. 6 shows a top view of the wafer container inserted into a shippingcontainer, in accordance with additional aspects of the presentinvention. More specifically, the shipping container 26 can be any knowncontainer used to ship wafers, e.g., plastic containers with a diameterof about the size of the wafers, themselves. The wafers 20 are placed inthe wafer container 10 and thereafter placed in the shipping container26. In this configuration, the straps 14 include the tabs 14 a′ for easeof handling, and slits 16 in order to attached adjacent straps to onefor shipping. The force distribution plates 24 can be implemented inthis aspect of the invention.

FIG. 7 shows a side cross-sectional view of the wafer container insertedwithin a shipping container, in accordance with additional aspects ofthe present invention. In this implementation, two force distributionplates 24 and the stack of wafers 20 (separated by the sheets 22) areplaced within the wafer container 10. The force distribution plates 24are provided on the top side and bottom side of the stack of wafers 20,and the wafer container 10 is placed within the shipping container 26.Foam cushions or sheets 28 can be provided over and under the forcedistribution plates 24, on opposing sides of the stack of wafers 20. Inoptional embodiments, one or more perimeter cushions or sheets 28′ areprovided about the edges or perimeter of the stack of wafers 20 toprevent lateral movement of the thin wafers during shipping. Also, inoptional embodiments, a reinforced cover 30 is provided on the upperfoam cushion 22 to provide added protection during shipping.

As represented by FIG. 8, the shipping container 26 can be assembled asfollows:

(i) the straps of the wafer container are spread out, allowing access tothe bottom surface;

(ii) a lower force distribution plate is placed on the bottom surface ofthe wafer container;

(iii) a plurality of wafers and sheets are alternately stacked on thelower distribution plate, on the bottom surface of the wafer container.The wafers can be stacked (and unstacked) using a conventional vacuumwand;

(iv) an upper force distribution plate is placed on an uppermost sheetof the stack of wafers;

(v) at any stage before, during or after steps (i)-(iv), a foam cushioncan be placed on a bottom of the shipping container. At similar stages,in optional embodiments, the perimeter foam cushions can also be placedin the shipping container;

(vi) the straps of the wafer container are grasped by a user, e.g., thestraps are held together above the upper force distribution plate;

(vii) the user picks up the wafer container, using the straps, andplaces the assembly within the shipping container (on the foam);

(viii) the user folds the straps in the manner already described herein;

(ix) upper foam is placed on the wafer container, above the upper forcedistribution plate;

(x) in embodiments, a top cover can be placed on the upper foam; and

(xi) the container is sealed.

The wafer shipping container may then be disassembled by reversing theassembly process. It should be understood by those of ordinary skill inthe art, that the unloading (unpacking) process does not necessarilyrequire removal of the lower distribution plate, the lower foam sheet orthe perimeter cushions.

Table 1 shows testing performed on 100 micron, 85 micron, 75 micron and65 micron wafers. As shown in this table, each of the wafers passed alltesting: downward pressure test, vibration test and drop test.

TABLE 1 Wafer Thickness Downward (microns) pressure Test Vibration TestDrop Test 100 microns  Passed Passed Passed 85 microns Passed PassedPassed 75 microns Passed Passed Passed 65 microns Passed Passed Passed

The method(s) as described above is used in the fabrication ofintegrated circuit chips. The resulting integrated circuit chips can bedistributed by the fabricator in raw wafer form (that is, as a singlewafer that has multiple unpackaged chips), as a bare die, or in apackaged form. In the latter case the chip is mounted in a single chippackage (such as a plastic carrier, with leads that are affixed to amotherboard or other higher level carrier) or in a multichip package(such as a ceramic carrier that has either or both surfaceinterconnections or buried interconnections). In any case the chip isthen integrated with other chips, discrete circuit elements, and/orother signal processing devices as part of either (a) an intermediateproduct, such as a motherboard, or (b) an end product. The end productcan be any product that includes integrated circuit chips, ranging fromtoys and other low-end applications to advanced computer products havinga display, a keyboard or other input device, and a central processor.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A package assembly comprising: a container havinga plurality of straps attached thereto; at least one force distributionplate positioned in relation to the container; a stack of waferspositioned above the at least one force distribution plate; and at leastone foam cushion contacting the at least one force distribution plate.2. The package assembly of claim 1, wherein the container comprises anelectrostatic discharge (ESD) compliant material.
 3. The packageassembly of claim 1, wherein the straps are hinged or flexible.
 4. Thepackage assembly of claim 3, wherein each of the plurality of straps isspaced equidistance from one another about the bottom surface.
 5. Thepackage assembly of claim 1, wherein the plurality of straps includetabbed portions.
 6. The package assembly of claim 1, wherein theplurality of straps include slits.
 7. The package assembly of claim 1,wherein the at least one force distribution plate is positioned withinthe container.
 8. The package assembly of claim 7, wherein the at leastone force distribution plate is structured to: distribute forces over astack of wafers within the container; and contain the stack of wafers asa unit allowing them to move as a unit.
 9. A package assembly,comprising: a wafer container having a plurality of straps extendingtherefrom; a stack of wafers positioned within the wafer container; oneor more foam cushions or sheets positioned about the stack of wafers;and a force distribution plate positioned beneath the stack of wafersand contacting the one or more foam cushions or sheets.
 10. The packageassembly of claim 9, wherein: the wafer container compriseselectrostatic discharge (ESD) compliant material; the straps are one ofa hinged and flexible material; and each of the plurality of straps isspaced equidistance from one another about the bottom surface.
 11. Thepackage assembly of claim 9, wherein straps of the plurality of strapsinclude at least one of tabbed portions and slits.
 12. The packageassembly of claim 9, further comprising: a shipping container whichholds the wafer container; and upper and lower foam cushions or sheetspositioned above and below the wafer container.